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FAQs on Freshwater Substrates: Chemical Properties

Related Articles: Freshwater Substrates, Nice bottoms; Choosing the right substrate for your aquarium by Neale Monks, Freshwater Deep Sand Beds Work by Deirdre Kylie, Setting up a Freshwater Aquarium, Tips for Beginners

Related FAQs: Freshwater Substrates 1, FW Substrates 2,
FAQs on: FW Substrate Selection, FW Substrate Physical Properties, FW Substrate Amounts & Placement, FW Substrate Changing, Moving, Adding To, FW Substrate Cleaning, FW Substrate Issues, FW DSBs,

Some substrates are chemically inert... You may well want yours to buffer your pH, even add alkalinity. These properties can be tested for by soaking some gravel in pure water and measuring in a few days w/ test gear

Rising ph with black gravel    7/15/12
I have recently setup my new 55G tank and I am using black gravel - I have done the tests on it with vinegar and nitrate bottle #1 and it does bubble on both tests - my query is I know it is causing my ph to rise but by how much I don't know - in the last 5 days it has gone up from 7.4 - 7.65 - will the rising stop or is it going to be a continual rise
<Can't tell on the basis of the information presented... but not likely much more>
 - other tests show
GH 7
KH 6
Nitrate - 0
Nitrite -0
Ammonia - 0 - .25
Phosphate - well over 10
<!?>

caused by Seachem neutral regulator - I tried this on recommendation from LFS to no avail - I am going to run Phos guard to get it back down - how can I maintain a steady ph without it fluctuating up and down -
<Mmm, not hard to do... likely the gravel will dissolve at some rate to maintain pH in the sevens...>
if I have water treated down to ph 6.5
<How and why?>
 and add it with the gravel will it rise by a certain amount (.75 ph) or will it raise to a certain ph (7.7)?? I hope all this make sense :) - I have 2 large pieces of driftwood in the tank and may run Eheim peat in a filter to see what effect it has - fish are 8 Serpae tetras 8 head and tail light tetras 10 cardinals 2 clown loaches 2 bristle nose cats 4 sterba Corys 1 Redtail black shark 2 Bolivian butterflies 3 Kribensis 4 silver sharks 6 rummy nose tetras - all very small fish at the moment - am I correct in saying I need to lower the KH to be able to make any change in the ph?
<Mmm, well; this is quite an eclectic mix... the loaches and minnow sharks like harder, more alkaline water... the small characins softer and acidic... In a perfect world I'd suggest you set up another tank and separate the two groups (there's going to be trouble compatibility wise in time anyway), and seek out other black gravel (there are some that are chemically inert...) and keep the two groups separately>
Thanks in advance
Simon
<Welcome. Have you read here: http://www.wetwebmedia.com/FWSubWebIndex/fwph,alk.htm
and the linked files above?
Bob Fenner>
Re: Rising ph with black gravel    7/16/12

> Hi Bob - thanks for the quick reply -
<<Welcome>>
> I have recently setup my new 55G tank and I am using black gravel - I
> have done the tests on it with vinegar and nitrate bottle #1 and it
> does bubble on both tests - my query is I know it is causing my ph to
> rise but by how much I don't know - in the last 5 days it has gone up
> from 7.4 - 7.65 - will the rising stop or is it going to be a continual rise
> <Can't tell on the basis of the information presented... but not likely
> much more> << *Will monitor for the next few days and see - I have been
> told by one place it will keep rising and then another said it will rise by .5 ph??>>*
<<Can't tell... but doubtful... was/is this a marine-system-intended substrate?>>
>  - other tests show
> GH 7
> KH 6
> Nitrate - 0
> Nitrite -0
> Ammonia - 0 - .25
> Phosphate - well over 10
> <!?> << *I was told that Seachem neutral regulator has caused the phosphate to rise??>>*
<<Ahh, yes; this will do it... many are phosphoric acid-based>>
> caused by Seachem neutral regulator - I tried
> this on recommendation from LFS to no avail - I am going to run Phos
> guard to get it back down - how can I maintain a steady ph without it fluctuating up and down -
> <Mmm, not hard to do... likely the gravel will dissolve at some rate to maintain pH in the sevens...>
> if I have water treated down to ph 6.5
> <How and why?> -* <<for testing purposes only using ph down>>*
<<I see>>
>  and add it with the gravel will it rise by a certain amount (.75 ph) or
> will it raise to a certain ph (7.7)?? I hope all this make sense :) - I
> have 2 large pieces of driftwood in the tank and may run Eheim peat in
> a filter to see what effect it has - fish are 8 Serpae tetras 8 head
> and tail light tetras 10 cardinals 2 clown loaches 2 bristle nose cats
> 4 sterba Corys 1 Redtail black shark 2 Bolivian butterflies 3
> Kribensis 4 silver sharks 6 rummy nose tetras - all very small fish at
> the moment - am I correct in saying I need to lower the KH to be able
> to make any change in the ph? <<*Is this correct about lowering the KH??>>
<<Likely so... put another way, lowering pH (in a few ways) will lower kH>>
> <Mmm, well; this is quite an eclectic mix... the loaches and minnow sharks
> like harder, more alkaline water... the small characins softer and
> acidic... In a perfect world I'd suggest you set up another tank and
> separate the two groups (there's going to be trouble compatibility wise in
> time anyway), and seek out other black gravel (there are some that are
> chemically inert...) and keep the two groups separately> *<<I am working
> on a second tank setup at the moment to split the groups - the LFS here in
> Melbourne Australia said all these species would be fine in my current
> setup - I showed them the full list before purchasing and two reputable
> shops gave the ok - I am not sure if the locally captive bred fish here are
> more tolerant of water conditions but there have been no issues in my tank
> thus far and all appear to be healthy and happy??>>*
<<They may be more tolerant given captive production, but will not prove compatible w/ growth. BobF>>

Freshwater Tank Setup with Coral Sand PH too High   5/31/11
Hello,
<Hello,>
I was wondering what you would recommend that I could do in order to lower the PH in my tank.
<Remove the coral sand. It has no place in an aquarium like this.>
Unfortunately I was sold coral sand for setting up a planted freshwater community tank. Now that it is setup and all plants and fish, driftwood, rocks, etc. are in the tank I don't want to go through the process of taking everything out of the tank, including the fish who may die in the process to replace the substrate with gravel.
<No, no risk of that. Remove the coral sand. Then, over the next few weeks, replace 20% of the water as per normal each weekend, and you should find that as the pH and hardness changes, the fish adapt just fine.>
My PH hovers between 8 and 8.4 and a bunch of my fish have died because of it, tetras, catfish, platies, etc.. The PH of my tapwater is about 7.7 and I believe most of those guys would live if my PH stayed in that area.
<Now, like most beginners you're concentrating on pH, which isn't the key thing. Hardness is what matters! Let's assume you have hard water. That being the case you want to choose species that thrive in hard water or tolerate hard water. Livebearers and Rainbowfish are consistently good choices, and among tetras, species such as Bloodfins, X-Ray Tetras and Penguin Tetras are notable for their tolerance of hard, alkaline water.>
I have a large piece of driftwood in my tank (56 gallon bow tank) and I did some research and found that adding driftwood can lower the PH.
<Yes, but not in hard water, unless you have tons of the stuff!>
One question that I have is will adding more driftwood to the tank, counter act the PH raising effect of the coral sand?
<Won't work.>
If not is there anything else I can do, as I have tried chemicals such as Neutral Regulator from SeaChem and that seems to do nothing to help the situation.
<Yikes! Don't try and change pH before altering water chemistry first. In this case, remove all the coral sand so that the water hardness drops, and then accept the hard water you have from your tap water. Determine its water chemistry, then choose species for your community accordingly.>
Any information would be greatly appreciated!
<Read: http://www.wetwebmedia.com/fwsubwebindex/fwh2oquality.htm
>
Thanks,
Eddie
<Cheers, Neale.>

Garnet Sand as Substrate
Garnet Sand In an Aquarium - 2/7/10

Hi, There's a location nearby where sand was laid down for a forest service
dirt access road long ago. In one section the sand is 80-90% garnet, and is a beautiful dark purple color. I've been considering using it in an aquarium, most likely as a top layer on Eco-Complete, but I haven't found any references online to people using it. I wouldn't take enough to compromise the road, and could even replace it with sand similar to what was used everywhere else.
Chemically it seems close enough to normal silica sand to not be too abrasive, and it feels smooth enough to not being a problem. Average particle size is three or four times larger than play sand. I was curious if you'd heard of anyone else using it, and if you could foresee any problems beyond the standard anaerobic bed/hydrogen sulfide and diatom bloom problems sand can have.
If I do end up using it the plan is to wash it like crazy with a bucket and hose to get rid of all the organics and small particles, then bake it to sterilize.
Thank you, and thank you for excellent help on a previous question.
Matt Williams
<Most gravels and sands sold for the construction trade have a pretty good durability index and are really hard. These usually don't break down with heavy traffic driving on them. I would recommend washing it in a bucket until the water runs clear. Fill a glass with half of the material and then fill the glass with distilled water. Measure the pH of the water in the glass to see if the material reacts with the gravel. If there is no change after a week I would say that it is good to go.-Chuck>

Will Synthetic gravel contaminate water quality and affect Flowerhorn 12/12/09
Hi there
I have 2'' Short-Body Flowerhorn in 40 gallon tank. Recently I have bought synthetic colored gravel to décor my fish tank. Unfortunately color of the gravel is fading. And also small particles of the colors are floating.
<Sounds very cheap, very badly made gravel. Remove. Ordinary lime-free gravel is by far the best substrate. Coloured gravels stress the fish, so their colours are less good. Cichlids adjust their colours: the darker the substrate, the stronger their colours. Silly red and blue gravels might appeal to (some) fishkeepers, but fish HATE them.>
Could you tell me it will cause any problem to my baby Flowerhorn.
<Cheaply made gravel may well leach dyes and other chemicals into the water. In theory at least, cheap paints could be toxic (see for example the lead paint issue with Chinese toys). This will not be a problem with generic, lime-free gravel.>
So far My Baby FH is very active and eating normally. Please give me your suggestion. I'm so worried of it.
Thanks in advance
Push
<Cheers, Neale.> 

55 gallon FW Stocking
Sand , Jurupari and Rainbow Questions   4/9/09

Hello Crew and Thank You for a great job.
I'm going to set up 55 US gallon FW tank and have some questions about this.
I want to put sand on the bottom. Home Depot sells sand for "playground".
They do not specify, what kind of sand is that. Do you have any idea if this sand is safe for a fish tank?
<In different areas of the country the sand may be different. Get a small sample and place in it some distilled water. If the TDS or pH changes then the material is leaching minerals into the water and is generally not good for use in an aquarium.>
I'd like to keep in the tank 2 Geophagus jurupari.. I do not see a lot of information about this fish. Some of the internet sites say they are very touchy and require very soft water. I assume my water is very hard (pH=8).
Are they really need soft water like discus or rams?
< Wild Satanoperca jurupari do come from areas of soft acidic water. Most of the fish today are tank bred and do much better in harder water. They may be maintained in harder water but will probably not breed.>
If that the case, I better choose different species. Please let me know, if they will adapt to a hard water.
Also would it be aggression problem between 2 Geophagus jurupari?
< They are not an aggressive species. Keep in mind that any eartheater type of cichlid will constantly be sift food from the sand. If the sand is too coarse or has angular edges then it will be abrasive and cause disease problems.>
I also want to keep 6 boesemanni Rainbowfish. If I buy 6 juveniles, would it be a problem, if I will get more males than females?
<Rainbows will be fine in a group. Males will show their best colors with some females around.>
I want to plant the tank with different kinds of Anubias, and I want to add gold nugget Pleco. Is it safe to keep this Pleco with Anubias?
< There are many types of gold nugget Plecos with different requirements.
Go to Planetcatfish.com and research the species of Pleco you are looking to get.>
What do you think about this stocking overall? Will this system work?
< The Pleco will probably be wild and may need soft acidic water. The rainbows on the other hand like hard alkaline water. Maybe look at something like Congo tetras if you are going to soften the water or get a common Pleco that will tolerate the harder tap water.-Chuck>
Thank you, Mark

For Neale: Follow-questions. Stkg. FW, substrates...  7/10/08 Dear Neale: I am working on TWO aquarium projects, and much of what I'm trying to do is based upon previous suggestions/ideas that you provided. I was sort of "challenged" by your suggestions, so I'm stepping out of my comfort zone to get my feet wet (hee hee) in some areas of aquaria that I've not previously entered. The current stocking plan for my 125-gallon (72" long) freshwater aquarium is: --School of tiger or ruby red barbs, (or OTHER small barb, if necessary to make this work). --Three or five South American Pufferfish. --Unsure about bottom-dweller(s). --AS A RULE, I'm trying to follow your suggestion for choosing a top-water species, a mid-water species, and a bottom-dweller species. I have never kept puffers. If they are considered to be mid-water-dwellers, then I realize that I have chosen TWO mid-water-species, as I desire to have the barbs AND the puffers, if possible. <Puffers aren't really midwater fish; they swim at all levels, and more specifically, close to solid objects that they scan for food.> I am struggling over the issue of substrate, as I like the attributes of the sand that YOU use in your aquarium, but I would truly prefer DARK-colored substrate. You made the comment that the black Tahitian Moon Sand is "sharp" and not suitable for certain bottom-dwellers. Taking that into consideration, I'm wondering if I may use the Tahitian Moon Sand, and simply avoid those "certain bottom-dwellers". <This is precisely what the manufacturers of this sand state: unsuitable for bottom dwellers. For midwater fish like barbs and tetras, Tahitian Moon sand is just dandy.> That idea raises a couple of questions: --You mentioned that your puffers curl up, on the bottom, to sleep at night. Is this sand too sharp for them to do THAT? Are there any other reasons that puffers would not do well with sharp sand? <Hmm... not sure it would do them much harm. They tend to just rest on the substrate in my tank. That said, other aquarists have reported Colomesus burrowing into the sand itself. So it's a bit of a gamble.> --Is this sand too "sharp" for fish to touch it while picking up morsels of fallen food, that are laying upon the substrate? <Should be fine for this. The problem is more for fish that go into the sand (e.g., Spiny Eels) or constantly push it through their gills (e.g., Corydoras).> --Are you able to suggest any bottom-dwellers that would be FINE with this sharp sand, or if using this sand, is it best to simply avoid bottom-dwellers altogether? <I'd concur with the manufacturers and simply avoid bottom dwellers. I don't want to be blamed for secondary bacterial infections on your fish any more than CaribSea!> --*As an alternative*, I saw a suggestion on a discussion board for using dark colored "sand" that is intended for sand blasting. This stuff is smooth/round. Do you happen to know if that substance is inert? <I think you'd have to research whatever sand is being sold for this purpose. There's no blanket recommendation that I'm aware of. As always, you can test for lime using an acid to see if the sand bubbles (if it does, there's lime in the sand, and it's no use for a neutral/acidic aquarium). Personally, I prefer to use safe silica sand, and then rely on adding gravel and/or low level plants to reduce the brightness. Seriously, with a bit of gravel and a thick jungle of Cryptocorynes, the sand is much less objectionable (and much more realistic) than you'd imagine.> If I can work through these few issues, I believe I'll be prepared to purchase the balance of my supplies, and proceed with this project. I have a couple of questions about my other aquarium project, but I don't want to "clutter" this message with that, so I'll send it at another time. AS ALWAYS, I am very grateful. Oh yes -- I almost forgot. Have you authored any (freshwater) books that include information for intermediate and advanced aquarists? At this point, I am particularly interested in YOUR approach to things, as my appetite has been wetted by W.W.M. articles that you've written. Thank you. Jake <Jake, all my freshwater stuff has been online and in magazines. I haven't yet authored anything on freshwater tanks. Plenty of excellent authors out there already! Best wishes, Neale.>

Re: For Neale: Follow-questions, sand...  7/10/08 Dear Neale, Thank you for your excellent input. With these alternatives, I'm prepared to give up on the "sharp" sand. (I had a difficult time letting that one go!) Onward and upward! Jake <Suspect your decision here is a good one. Cheers, Neale.>

pH Level While Using Red Sea Floralbase 11/07/07 Hi, I have recently set up a new 72gal FW tank. I have had water in it, Rena xp3 filter, heater, and Corallife 65watt x2 for lights. I presently have 15 goldfish in it to help with the cycling. <<A poor idea. Too much stress and likelihood of parasitic infestation... RMF>> My ph level has been at 6.0 from the start. I am using red sea Floralbase, that's all, as I have a planted tank. I am wondering how to raise the PH level to at least 7.0 for the types of fish I want (I have a 10gal that has been established for 2 years now & I would like to take those fish and move them over to the new one, that PH has been 7.0 - the fish in the 10gal is neon tetra, black skirt tetra, 2 Danios and 1 Chinese algae eater). Is there some sort of PH up that I can use safely? I do have several kinds of plants. My ammonia, nitrites and nitrates are all within the proper range & are great. Thanks Kim <Hello Kim. Two things here. Firstly, what sort of fish do you want to keep? An acidic pH of 6.0 is actually very good for a wide range of species. Most South American fish will thrive here, as will most of the fish from Southeast Asia. Secondly, you need to clear up the difference between pH and hardness in your head. Fish don't "feel" pH directly and don't really care about it all that much; what matters is how much mineral content the water has, because this is what has an impact on osmoregulation (how they balance salt and water in their bodies). So, what you want to check first is the hardness of your water now, and the preferred hardness of the fish you want to keep. I'm guessing your water is quite soft (i.e., a low hardness around 5 degrees dH). That's fine for tetras, angelfish, Gouramis etc. But if you want to keep livebearers or Rainbowfish, they need a higher level of hardness, at least 10 degrees dH and ideally well above that for livebearers especially. Once you take care of hardness, then the pH will adjust itself pretty well automatically. Hard water tends to have a high pH, and that high pH is pretty stable. There are various ways to raise the hardness. The simplest is to incorporate some calcareous material into the filter. Crushed coral is one such medium. As the water washes past, the coral dissolves, raising the hardness. Periodically you clean the coral to wash away slime that coats it, and maybe once a year replace it with a bunch of new coral. There are other methods too; any aquarium book should discuss them, but if you want some more ideas, let me know. Cheers, Neale.>

Just a question... Rocks from the beach, use/FW  -- 09/14/07 Hi I own a ten gallon tank and I found some stones on the beach and was wondering if I could put them I the tank? I have platies and tetras. If I can put them in what are the procedures for doing so? <Depends on the stones. If they're non-soluble, non-porous things like granite or flint, then simply washing well with hot water should make them adequately safe. Anything soluble, like limestone or coral, is less useful because these will change the pH and hardness of the tank (to test, add some acid: if there's fizzing, the rock contains lime). The platies won't mind, but the Neons will. So these sorts of rocks shouldn't be used. Porous rocks, like pumice, are generally best avoided because anything dead in the holes can decay in the aquarium and pollute the water. If in doubt, leave the stones out and just use ones bought from a tropical fish store. In a 10 gallon tank especially, hollow ornaments would displace less water and create hiding places for your fish, particularly baby platies. As such, they'd be much better value. Cheers, Neale>
Re: Just a question... testing FW substrates  -- 09/14/07
Thank you Neale, but how long should I soak them in the vinegar for? I tried and only one to three bubbles came up, so I put them in the tank is it alright? <No, you don't soak in acid. You add acid (like vinegar) and if there are bubbles, that means the stone contains lime. Lime + acid = carbon dioxide. The conclusion is you CANNOT use this stone in a freshwater aquarium. If you put it in the aquarium, it will slowly dissolve raising the pH and hardness. Cheers, Neale>

Reefbase Coral Sand for FW use?    5/14/07 A friend of mine just got a new saltwater tank and it came with a starter kit -- Sand, chemicals, etc. The sand is Reef Base (made by Red Sea ) Crushed Coral and I was curious if I could use that in a freshwater tank. Thanks, Tony Zucarelli <Can be... if the livestock you intend to keep likes/tolerates hard, alkaline water... the CaCO3 will continuously dissolve... Useful for some types/biotopes... Please read here: http://www.wetwebmedia.com/FWSubWebIndex/fwsubstrates.htm and the linked files above. Bob Fenner>

Snails and Sand - 05/10/2006 Hello, I have learned so much from the information you provide on you website.  Learn something new everyday they say.  Wow!!....that's an understatement. <Excellent!  Thank you for these kind words.> My question is this... I came across a bag of Bone Aid Calci-Sand, T-Rex brand, pure natural calcium carbonate substrate.  Would this be something I could add to my snails tank?   <I wouldn't.  This will significantly change the pH and alkalinity of your water.> It appears to be for reptiles.  If it is alright for my freshwater tank, how much should I add and how would I add it to the tank? <Unless your tank's inhabitants want/need a very high pH and alkalinity, this is not a good plan.> I have a very handsome Golden Apple Snail, Dale.  I take very good care of Dale and his 10 gallon aquarium.  Dale has a heater, filter, bubbler (which he plays on), and a pump.   <Sounds great!> His shell is growing so much, I'd say about a half inch of new so far.  He amazes me. <Sounds like he's a pretty happy snail.> I'll look forward to hearing from you. <For now, I'd suggest to leave well enough alone, and not add this to your tank.  Sudden changes in pH are not good for your critters.> Thank you for your time and expertise,  -Jill <And thank you again for your kind words!  Wishing you well,  -Sabrina>

Crushed coral in freshwater tank? (03/02/03) <Hi! Ananda here today...> I am setting up a 55 gal. tank that was used sometime in the past for saltwater. The guy that I bought it from said that he used it a couple years for FW, and took it down when he acquired a larger tank. Not having any aquariums for several years, I was eager to get started, but having found your website I quickly learned how much I didn't know about a former hobby! <Yep, a lot has changed in the past few years....> I thoroughly cleaned everything with bleach/water, and soaked the gravel (which I now know is crushed coral) in bleach-water overnight, followed by a fresh water rinsing & picking out of many snails. I have the tank test filled, filtering and aerating while awaiting arrival of test kits, etc. Having found your invaluable site while scouting for needed supplies, I spent hours (literally) reading the FAQ's, and perhaps saving my future sanity while avoiding some expensive mistakes already. <I wish I had found this site before I got started! Glad it's saved you some money already. But I think sanity is over-rated.> I now have a 10 gal. set up for future use as a quarantine tank, and will concentrate on getting it properly cycled first. <I wish more people would quarantine their freshwater fish. Kudos to you.> I have not been able to find any reference to using the crushed coral in FW, but after reading advice on saltwater ornaments, I see a red flag. <Yup, big red one, unless you want to keep African cichlids -- in which case it's a big green flag. Crushed coral will raise the pH in your tank as it dissolves. If you have enough crushed coral in the tank, your pH can go above 8.0!> Your thoughts and comments would be much appreciated. <Keep researching and reading, and we have a couple of freshwater forums on the WetWebFotos discussion boards -- I check those frequently, as do others with more freshwater expertise.> Thank you. Jess <You're welcome. --Ananda>

- Crushed coral raising pH? - I'm sorry to bother you, but I am totally lost amidst the bewildering array of contradictory information I'm receiving regarding my freshwater tank. Here's my situation: My pH is high and I'm not sure what to do about it. I have a 37 gallon Oceanic tank that has both fish and plants. My substrate consists of gravel/rock and crushed coral for color. <Ding ding ding!> For plants, I have two Amazon Swords, a pygmy Sword, Anubias, Rotala Indica, and Apon. bolivianus. I have 8 Danios (4 leopard and 4 zebra), 15 Neon Tetras, 5 Golden White Clouds, 2 German Rams, and a Gourami. Today I did a 20% water change that brought the pH down to about 7.8 from a high of 8.3. <Ironically the proper pH for marine aquaria> Since I'm a newbie, I hesitant to do anymore water changes for fear of ruining a newly cycled tank. I would rather not force the pH down by using chemicals. I've got conflicting advice. Some say remove the coral, others say leave it, and still others say everything will be fine. <It's the coral that's doing it. It is slowly dissolving and increasing both your carbonate hardness and pH. You'll have a hard time getting it down with chemicals since it will just jump back up. I guarantee you, if the new water you add for water changes and top-off has a neutral pH, once you remove the coral you will have no more problems. Enjoy! -Kevin> Tom

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